Shower Pre-Slope Help

I'm finishing my basement and will be (hopefully) putting in a shower pre-slope, liner and tile base this weekend. The basement floor is concrete. I've adjusted the drain location based on how the bathroom was framed and installed the necessary P-Trap. It's not quite centered but pretty close.

As I get started, I have a couple questions:

1. I've left the drain pipe longer than it needs to be because I wasn't sure if it should be flush or something different. I believe if I cut it flush, my drain flange will sit about 1.25" above the floor. Is 1.25" good for the center pre-slope eight, or should I make it lower or higher? I left room around the drain in the floor so it could sit below the cement about an 1" if needed.

2. I believe I should finish the shower floor before installing the wall material to reduce likelihood of mold on the walls. But I've seen videos that install the pre-slope, liner and tile base with the walls on. Appreciate any opinions on this.

3. I likely won't be tiling for a few weeks yet, maybe a month. Does waiting before I put tile on somehow affect the integrity or curing of the floor? I've read that I should tile right away (within a day or two) or wait 28 days or longer.

I've used 2x8s around the base of the shower frame to reinforce the framing, which I'm not quite done with yet (as you'll see in the picture).

Thanks for any help or other advise you can provide.